76 NATURAL SCIENCE. Feb., 



block, of which any quantity can be obtained, is an altered limestone 

 which occurs fragmentarily in the pumice of the series of explosions 

 that excavated the Atrio del Cavallo, known as Phase VI, period 4, 

 and Phase VI, period 1 (Plinian eruptions) of Johnston Lavis. 

 Eozobn canadense, therefore, in the view of these authors, is nothing; 

 more than the zonal alteration of blocks of limestone which have 

 been enclosed in an igneous magma, a view also supported by its 

 mode of occurrence in Canada and elsewhere. These specimens are 

 fully described and beautifully illustrated by photographic plates in 

 the memoir before us (" Eozoonal Structure of the Ejected Blocks of 

 Monte Somma," Scientific Transactions of the Royal Dublin Society, vol. v., 

 series 2, October, 1894), an< ^ to this paper we must refer the reader 

 for the details. 



Whatever may have been the past history of the dispute, we at 

 present cannot regret it, for it gave rise to a long series of interesting 

 papers, and called forth such an amount of research into organic and 

 inorganic structures as no other object has succeeded in doing. At 

 the same time, it teaches that extreme caution is necessary when 

 dealing with structures difficult of explanation and presenting pecu- 

 liarities at once characteristic of biological and petrological forms ; and 

 while it urges less dogmatism, it shows how necessary it is for the 

 specialist in one branch to call to his aid specialists in other branches, 

 even when examining a structure which appears so obviously to 

 belong to forms with which he is familiar. 



Oolite. 



The singular resemblances which are seen between organic and 

 inorganic structures were well exemplified at the Geologists' Associa- 

 tion at its meeting on January 4. Mr. G. F. Harris read a paper 

 "On the Analysis of Oolitic Structure," during which he showed 

 upon the screen a series of photographs of microscopical preparations 

 of oolitic granules. One of these was a silicious sphere formed in the 

 warm waters of a pool in the Yellowstone district. Commencing as a 

 solid body, the sphere gradually became more and more cavernous, 

 and the outer layers bore a strong resemblance to the organism 

 known as Parkeria, from the Cambridge Greensand. These cavernous 

 modifications were probably due to the enveloping of small algae by 

 the silicious coats. Sections of granules were shown by Mr. Harris 

 from the Great Salt Lake, the extinct Lake Lahontan, the recent 

 oolite sand forming off the Bahamas, and from many localities of the 

 oolitic formation in England. The majority of these granules had 

 characters peculiar to their locality, and the lecturer was satisfied 

 that, so far as the English oolites were concerned, the nature of the 

 grains was sufficiently characteristic to enable him to refer with a 

 considerable degree of certainty specimens of the rock to special 

 localities. The paper dealt only with the structure of the grains, but 



